Spray coating system



A ril 16, 1968 Original Filed June 10, 1966 mmmmm J. w. JUVINALL ET AL 3,377,987

SPRAY COATING SYSTEM 5 Sheets-Sheet 1 LO N INVENTORS JANE W JUl/l/VALL BY CHESTER A. PURDY Attorneys April 1968 J. w. JUVINALL ET AL 3,377,987

SPRAY COATING SYSTEM 5 Sheets-Sheet Original Filed June 10, 1966 m O v/ E E W M VV N w A 6m ME Mm Y mm B wv on m v Q on we m N M iv m mm m? 8 mm m m mm mm 6 km nmv O A/rorneys April 968 J. w. JUVINALL ET AL 3,377,987

SPRAY COATING SYSTEM 5 Sheets-Sheet 5 Original Filed June 10, 1966 INVENTORS JAMES W. JUVl/VALL BY CHESTER .4. PURDY A/larneys United States Patent 3,377,?87 SPRAY (DATING SYSTEM James W. .luvinali, Indianapolis, Ind, and Chester A.

Purdy, Belmont, Wis, asslgncrs to Ransburg Electro- Coating Corp, a corporation of Indiana firiginal application June 10, 1966, Bar. No. 556,779, new Patent No. 3,320,975, dated May 23, 1967. Divided and this application Oct. 21, 1966, Ser. No. 623,477

10 Claims. (Cl. 118-626) This is a divisional application of Ser. No. 556,779 filed June 10, 1966; now Patent No. 3,320,975, granted May 23, 1967.

This invention relates to a spray coating system, and more particularly to an improved system for controlling the rate of atomization of a liquid COating material, as in an electrostatic painting system.

In certain operations using a How of liquid under pressure, as for example production line electrostatic spray painting, it may be desirable to vary the rate of atomization of the liquid, as for example when painting of a different surface area, or when it is desired to change the thickness of the film deposited on the article surface. In automatic production line electrostatic spray painting, once the proper atomization rate has been determined for a given type of article, it is desirable that this atomization rate remain unchanged. However, changes in temperature of the paint caused by changes in ambient temperature, or changes in the amount or type of solvent, may make appreciable changes in viscosity of the paint being sprayed.

One feature of this invention is that it materially minimizes chan es in liquid flow in the system which might otherwise occur as a result of changes in viscosity of the liquid, providing a control system which is relatively insensitive to viscosity changes;

Another feature of this invention is that it provides a flow control orifice which is open, in the sense that the:e is no central needle valve member, and yet which may be adjustable to regulate the rate of flow of liquid therethrough at a given liquid pressure;

Yet another feature of this invention is that the control orifice has no dimension transverse to the direction of liquid flow which is more than a couple of dozen times the other dimension transverse to the direction of liquid flow, preferably no such dimension being more than a few times the other dimension, the best results being attained when the dimensions are about equal, as in an opening which is generally circular or relatively square;

A still further feature of this invention is that the system provides positive control of the rate of atomization of the liquid from the atomizing device, yet eliminates the need for positively acting pumps and fluid regulators heretofore used in the liquid lines; and

Yet another feature of this invention is that the adjustable orifice element is small in size, so that a plurality of such elements can be placed relatively close to the atomizing device where a plurality of liquid feeds are provided therefor, as in remotely controlled color change systems used in painting.

Other features and advantages of this invention will be apparent from the following specification and drawings, in which:

FIGURE 1 is an illustration in diagrammatic form of one type of electrostatic painting system utilizing this invention;

FIGURE 2 is a vertical sectional view of an improved valve forming part of the flow control system here disclosed;

FIGURE 3 is an elevational view of the valve shown in FIGURE 2, looking from the right of such figure;

FIGURE 4 is a detailed fragmentary view showing the 3,377,937 Patented Apr. 16, 1968 "ice way in which the effective orifice size of the adjustable oifice is varied;

FIGURE 5 is an illustration in diagrammatic form of another type of electrostatic painting system utilizing this invention;

FIGURE 6 is a vertical sectional view of another form of adjustable orifice valve; and

FIGURE 7 is a fragmentary vertical sectional view of a portion of the hand spray gun shown in FIGURE 5.

Referring now more particularly to FIGURE 1, a representative electrostatic spray painting system utilizing this invention is illustrated, one wherein change of color of the paint being applied may be remotely controlled by suitable means. A plurality of articles 10, as the articles Illa-19g illustrated, are grounded through and carried by a conveyor 11 which moves them at a predetermined rate from left to right, as the parts are illustrated in this figure. At a suitable distance from an article surface as it passes through the spray zone, as inches therefrom, is a rotating electrostatic atomizing device 12. This atomizing device is adapted to be rotated by the motor 13 and to have a high potential electrostatic field created between its edge and the article surface it confronts by a high potential power supply 14. When paint is supplied to the atomizing device the field atomizes the paint into a spray of line, charged particles which are then electrostatically deposited, while still liquid, on the article in the spray zone.

The particular system illustrated in FIGURE 1 is of the paint recirculating type. Paint in a paint reservoir 15 is forced by pump 16 through filter 17 and along pipe 18 through valve 19. Paint then returns through pipe 20, back pressure regulating valve 21 and pipe 22 to the paint reservoir 15. A pressure sensing conduit 23 is in communication with the pipe ahead of the back pressure regulating valve 21, and this conduit 23 provides pressure to a pressure control unit 24. This control unit operates through air under pressure supplied from line 25 to regulate the amount of restriction provided by back pressure valve 21, operating to maintain a desired pressure in the paint recirculating pipes at all times.

As Will be described in more detail in connection with subsequent figures, the valve 19 provides means for initiating and terminating paint flow through the feed tube 26 to the atomizing device 12, and for regulating the rate of such flow. A system is thus provided wherein paint at a predetermined desired pressure can flow through the valve 19 to supply paint to the atomizing device at a desired rate of flow, this flow being initiated and terminated from a remote location by admitting air under pressure through the pipe 27, or releasing air therefrom. In order to enable different paints, as paints of different color, to be supplied to the atomizing device 12 selectively as desired, additional valves 19 and 19" are illustrated. Paint at a desired pressure is supplied to each of these other valves by separate recirculating systems similar to the one just described, paint flowing toward the valve 19' through pipe 13 and returning through pipe 29', valve 19" similarly having paint supplied to it through the pipe 13" and returned to its paint reservoir through the pipe 20". When the valve 19' is opened by admitting air through the control pipe 27 it delivers a different paint through the feed tube 26 to the atomizing device 12; and when air is admitted to the control pipe 27, valve 19 supplies still a J illustration, and it will be understood that a dozen or more feed tubes and valves could in practice be associated with a single atomizing device to provide as many different paints as might be desired.

Referring now more particularly to FIGURES 2 and 3, the valve 19 is shown in detail. It utilizes a housing in which are contained both an adjustable flow regulating orifice and a remotely controllable on-oif valve. Pipes 18 and 2t) connect to the flow passageway 31 extending through the lower part of the housing, so that paint at the desired pressure is available in this passageway 31 at all times when the recirculating system is in operation, a removable plug 32 being normally sealed in place as shown.

Immediately above this plug and at the top of the passageway 31 is the on-olf valve member 33, here shown as seated on a seat member 34 here illustrated as an insert of suitable material, as nylon or delrin 500x. The valve member 33 is carried by a valve stem 35 extending slidably through packing means 36 and connected at its upper end to an operating piston 37, this piston being vertically movable in and suitably sealed with respect to the walls of the cylindrical upper portion of the housing 30. A member 38 in the housing above the packing material 36 serves as a gland member and as a support for the spring 39 normally urging the piston 37 to the uppermost position, as shown in FIGURE 2. A fluid opening 4-9 at the top of the valve housing is adapted to be connected to a controllable source of fluid under pressure, as the air line 27 illustrated in FIGURE 1, to provide remote control for the on-ofl valve 33. Under the effect of the spring 39, this valve 33 remains in the closed position illustrated until air under pressure is delivered to the opening 40, whereupon the piston is depressed and the valve 33 opened as long as suflicient fluid pressure is present. Openings 41 in the side wall of the housing beneath the piston prevent the trapping of air underneath the piston and enables free movement thereof upon the remote actuation of the device; and the openings provide outlets for paint, if the packing 36 should fail, preventing any chance of damage to the piston 37 and its packing.

An adjustable orifice fiow regulating valve is also contained in the valve housing, and comprises as its primary parts a vertically slidable plate member 42 and a cooperating generally cylindrical member 43. This cylindrical member is urged against the plate member by a spring 44 which contacts pusher member 45 engaging the lefthand end of the cylindrical member 43, as the parts are, viewed in FIGURE 2. In order to prevent rotation of the cylindrical member, it is provided with a pair of diametrically opposed slots 46 through which the stem 35 of the on-ofi valve passes.

The right-hand end of the cylindrical member 43, again speaking with respect to the position of the parts as shown in FIGURE 2, has a relatively large opening providing a thin plate-like portion 43a immediately adjacent the plate member 42; and, as may be best seen in FIGURE 4, this thin plate-like portion has ano pening 43b punched therethrough. The plate member 42 similarly has a thin platelike portion 42a having an opening 42b formed therethrough generally in registry with the opening 43b. The plate member 42 is slidable (vertically in the position of the parts as shown in FIGURE 2) and adapted to be manually adjusted to vary the amount of registry of the openings 42b and 43b, thus varying the size of the fiow control orifice and yet at all times leaving it open in the sense that there is no central needle valve member.

In the particular embodiment illustrated, adjustment of the plate member 42 is effected by having a cylindrical lower stem portion 420 threaded into the interior of a cylindrical member 46 which in turn is threaded into the housing 30 with a thread of difierent pitch than that with which it is threaded to the stem member 420. This differential thread arrangement provides for very small changes in registry of the openings 42b and 4311 upon roration of the member 46. While the openings are here shown as diamond shaped, the shape of the non-registering portions is not critical, whereas the portions in registry providing the flow orifice, particularly in the smaller amounts or registry of the openings, preferably should be so shaped as to approximate a square, :as by having the V-shape illustrated. In a satisfactory embodiment of this valve, the flow control openings are one-sixteenth of an inch square, although at normal flow control rates and pressures they might be in registry only to an extent providing an opening about .020 square, for example.

In order to minimize the effect upon flow rate of changes in viscosity of the liquid the plate sections in which these openings are formed should be quite thin, preferably of the order of a few thousandths of an inch thick. For best results the plate sections should each not be more than 50 thousandths of an inch thick, and preferably less than 20 thousandths of an inch thick, plates having a thickness between 3 thousandths of an inch and 10 thousandths of an inch having proved very satisfactory in operation. In order to have substantially the entire effect upon rate of flow achieved in this thin, open orifice, the passageways on each side thereof should have dimensions providing cross-sectional areas at least several times that of the maximum control orifice area which would be used. When the on-off valve 33 is in open position, all flow passage areas to the regulating orifice are at least several times that of the area of the'orifice; and the outlet flow passage 47 to a delivery tube or line also provides a relatively large area, as by being connected to a feed tube having an internal diameter of inch. While the two confronting surfaces about the openings 42]; and 431': are urged tightly into engagement by the spring 44, any chance of leakage around this orifice is obviated by use of O-ring seals 48 and 49. Similarly, the member 45 is provided with an O-ring seal 50.

In order to prevent drying of the plaint in or around the variable open orifice, it is preferable to arrange the system so that liquid paint is held in such manner as to completely fill the valve and the delivery conduit when paint delivery from that particular valve is terminated. In commercial practice, for example, the delivery conduit 26 (shown in FIGURE 1) would preferably be relatively short, as 8 or 10 inches in length, terminating in a capillary-sized delivery orifice of inch in diameter or slightly less through which paint would be delivered onto the rotating atomizing device 12. When the on-ofi valve 33 is in closed position, liquid paint would then be held in all passageways above this valve and in the delivery conduit by reason of the fact that in the absence of pressure paint would not flow through the capillary-sized delivery opening. This obviates drying out of the paint and clogging of the valve even if paint delivery through this particular valve should not be initiated again for a substantial period, as for a matter of hours.

The system heretofore described for the first time makes it practical to do multicolor electrostatic painting from a single atomizer. In the past electrostatic painting systems have used constant displacement pumps in order to get accurate control of the rate of paint delivery. It is impossible to locate a plurality of such pumps, or even a single pump, close enough to the atomizing device to sufiiciently minimize the amount of paint between the pump and the atomizing device when the pump is shut off. When such a pump was located any substantial distance from the spray device, there would be a considerable amount of paint in the hose leading to the spray device, and this would settle and result in a very poor initial color match when delivery of that particular paint was resumed. Furthermore, during periods of non-operation such pumps frequently permit the paint to seep back down the line, so that the lines do not remain full and must be refilled again when the pump is started, making it impossible to have an accurately timed on-off operation. The flow control system heretofore described, with the valves arranged within 8 or 10 inches of the atomizing device and the feed tubes having only one-eighth of an inch internal diameter, makes it possible to have as little as 2 cubic centimeters of paint between the on-oif valve and the discharge orifice; and the feed tube is kept full, so that reinitiation of spraying of that particular paint can be accurately timed. Moreover, the fact that there is such a small quantity of paint beyond the on-oif valve results in such a small initial deposit of paint, even if it has settled some, that subsequent paint covers the initial deposit and results in a satisfactory and uniform color in the finished coat.

Most prior painting systems have employed guns with needle valves for controlling the rate of flow of paint. In these systems, the paint was supplied under pressure from a circulating line or from a paint pot, and it was considered necessary to have a fluid regulator in the line. In order to minimize clogging in the narrow annular orifice of the needle valve, it was necessary to adjust the valve opening to the widest setting practicable, which in turn necessitated reducing the pressure of the paint to a low level, In such pressure systems, the circulating line or pot pressure was usually at least of the order of to pounds per square inch, and the pressure at the output of the fluid regulator was generally 2 to 3 pounds per square inch. The open orifice valve avoids clogging even at relatively small orifice openings, so that a higher paint pressure can be used. This not only eliminates the need for fluid regulators in the liquid lines, but is of particular importance in situations where the elevation of the spray device is changed materially during operation. Some painting systems mount the rotating atomizing device on a reciprocator having, for example, a vertical stroke of 5 feet. With the open orifice valve heretofore described, the paint can be placed under a pressure of or pounds per square inch with the clogging problem essentially eliminated even though the orifice area would be very small. Since change in rate of flow through such a small orifice varies substantially as the square root of the change in pressure, the approximate 2 /2 pounds of change in pressure resulting from the 5 foot change in elevation would, under such circumstances, result in only about a 2% change in rate of atomization of the paint, a change well within normal painting tolerances.

While the adjustable orifice illustrated and described is provided by openings in adjacent plates which are each only a few thousandths of an inch thick, it will be understood that the important factor in securing insensitivity to viscosity changes is having a relatively thin wall around the orifice. Accordingly, it is to be understood that this can be provided by using thicker plates suitably beveled toward the adjacent surfaces, although flat plates have the advantage of not changing Wall thickness if they are worn or abraded away, as by the paint flow. While the pair of confronting 90 V-shaped sections illustrated provide a square at any size opening to which the orifice may be adjusted, it will be understood that one dimension can be more than the other provided neither dimension transverse to the direction of flow is at any time less than 3 thousandths of an inch, and preferably not less than 5 thousandths of an inch. The insensitivity to viscosity change of the valve illustrated, with plates each about .004" thick, is such that with a particular paint and an adjustment of the valve providing 112 cubic centimeters per minute flow to the atomizing device, an increase in temperature from F. to 90 F. resulted in a flow increase of only 4%. Two different needle valves of the type heretofore used in painting systems, on the other hand, showed flow rate increases of 33 to 40% upon the same change in temperature of the same paint.

Another representative system in which the advantages of this invention may be utilized is illustrated in FIGURE 5. Paint in a reservoir or paint pot 60 has air under pressure thereover, as by having air admitted to the top of the pot from an air line 61 through an air pressure regulator 62. Paint at this regulated pressure (as for example 20# or more) is thus supplied through conduit 63 (which extends almost to the bottom of the paint pot) to valve 64, so that the rate of paint delivery is a function of the pressure of the paint and the effective opening of the orifice in the valve 64. The desired amount of paint is thus delivered through a flexible conduit or hose 65, which also carries the high voltage lead from the high voltage power supply 66, to the hand-gun 67. This is of a type known in the art, having a rotating atomizing device 68 adapted to have a high potential electrostatic atomizing and depositing field exist between it and a grounded article 69 which is being coated. In this system initiation and termination of paint fiow are effected by an on-off valve in the hand-gun operated by the trigger 70, as will be hereinafter more fully described, so that the valve 64 comprises only an adjustable open orifice in this case.

Referring now more particularly to FIGURE 6, a generally cylindrical member 71 is spring urged so that its end face contacts plate member '72. Each of these members have thin plate sections with openings of the character heretofore described in connection with the valve shown in FIGURES 2-4; and the position of the plate member is adjusted by the manually rotatable knob 73 to vary the amount of registry of the openings and thus the effective size of the thin plate open orifice provided. Paint supplied to the inlet opening '74 of the valve is thus delivered to the outlet opening 75 in an amount controlled by the pressure of the paint and the effective size of the control orifice. The seals and other details are generally similar to those heretofore described, except that in this valve only a single screwthread is used to determine the amount of registry of the openings, and is so arranged that the entire desired variation is obtained within 360 rotation of the knob 73, so that this may be calibrated conveniently by a single scale.

Referring now more particularly to FIGURE 7, the valving portion of the hand-gun 67 is illustrated in detail. Paint entering the hand-gun through the passageway 76 must pass the valve element 77 in order to flow through the passageway 78 leading to the rotating atomizing device. The stem of the valve element is movable through the packing 79, and a spring 80 urges the valve to closed position as illustrated in FIGURE 7. When it is desired to initiate paint flow, movement of the trigger 70 moves the valve element 77 off of its seat 81 and permits flow of paint. Except for a possible spotting or touch-up operation, the operator would in all cases move the trigger back to a position opening the valve fully so that paint flow would then be regulated by the adjustment of the valve 64, and would be relatively insensitive to viscosity variations. It is also to be understood that while a thin orifice is less sensitive to pressure variations than a needle valve, it provides sufficient variation that in many cases a fixed thin plate orifice may be used with such a hand-gun, as for example in the gun itself, with no need of adjustability of the orifice size. With a given fixed orifice, for example, variation of the air pressure in the pot from 5 pounds to 60 pounds varies paint flow from about 65 cubic centimeters per minute to 225 cubic centimeters per minute.

The system of paint fiow control disclosed in this application, with its thin open orifice valve, provides low sensitivity to viscosity changes, mild sensitivity to pressure changes, and non-clogging characteristics over a wide range of orifice sizes. These and other features of the systems heretofore described provide an improved spray painting system, with elimination of large and relatively expensive units heretofore considered necessary in spray painting.

While we have shown and described certain embodiments of our invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

We claim:

1. A system for painting articles, and comprising an atomizing device for atomizing paint supplied thereto, means to provide a supply of paint, a flow connection between the paint supply means and said atomizing device, an adjustable open orifice valve in said flow connection for controlling the supply of paint to the atomizing device, said orifice valve comprising a pair of mutually interrelated and relatively movable orifice sizing surfaces forming the adjustable opening in the open orifice valve, means for adjusting said orifice valve to regulate the flow of paint through the connection to the atomizing device, and means in said flow connection and independent of said open orifice valve and of said atomizing device for initiating and terminating fiow of paint to the atomizing device through said open orifice valve and positioned to maintain a sufficient head of paint in the flow connection on opposite sides of the open orifice valve both toward the atomizing device and toward the paint supply means for providing a quiescent supply of paint in said open orifice valve covering said orifice sizing surfaces when the initiating and terminating means is closed, thereby tending to prevent clogging of the open orifice valve.

2. A system for painting articles as claimed in claim 1, wherein there is provided means for electrostatically chargingatomized paint particles and for electrostatically depositing the particles upon the articles to be painted.

3. A system for painting articles as claimed in claim 2, wherein the charging and depositing means comprises a high potential field with an article as one terminal and with the atomizing device as the other terminal.

4. A system for painting articles as claimed in claim 1, wherein the initiating and terminating means is in the form of an on-off valve in the flow connection to the upstream side of the open orifice valve.

5. A system for painting articles as claimed in claim 1, wherein the initiating and terminating means is in the form of an on-ofi' valve in the flow connection to the downstream side of the open orifice valve for cooperation with the flow connection to the downstream side of the open orifice valve for maintaining the quiescent supply of paint in an amount flooding the open orifice valve.

6. A system for painting articles as claimed in claim 1, wherein the area of the opening through the adjustable open orifice valve is at all times a small fraction of the cross-sectional areas of the flow connection on both sides thereof.

7. A system for painting articles as claimed in claim 1, wherein the paint is supplied at substantially constant pressure and in an amount in excess of the atomizing requirements.

8. A system for painting articles as claimed in claim 1, wherein the initiating and terminating means is in the form of an on-ofi valve disposed in the flow connect-ion to the upstream side of the open orifice valve and with the paint in the flow connection to the downstream side of the open orifice valve under influence of gravity to maintain the sizing surfaces of the open orifice valve flooded when the onotf valve is closed.

9. A system for multicolor painting of articles, and comprising an atomizing device with connections to separate sources of diiferent colored paints, a separate flow connection between each source of paint and said atomizing device, an adjustable open orifice valve in each of said flow connections for controlling the supply of paint to the atomizing device, each said orifice valve comprising a pair of mutually interrelated and relatively movable orifice sizing surfaces forming the adjustable opening in' the constantly open orifice valve, means for adjusting each said orifice valve to regulate the flow of paint through its flow connection to the atomizing device, and means in each said flow connection independent of the associated open orifice valve therein and of said atomizing device for initiating and terminating flow of paint to the atomizing device and positioned therebelow to maintain a sufiicient head of paint in each fiow connection on opposite sides of the open orifice valve therein both toward the atomizing device and toward the paint supply means for providing a quiescent supply of paint in each said open orifice valve covering the included orifice sizing surfaces when the initiating and terminating means is closed, thereby tending to prevent clogging of each open orifice valve.

10. A system for multicolor painting of articles as claimed in claim 9, wherein each initiating and terminating means is in the form of an on-off valve disposed in the respective flow connection to the upstream side of the associated open orifice valve, and with the paint in each flow connection to the downstream side of the associated open orifice valve under influence of gravity to maintain the orifice sizing surfaces of each open orifice valve flooded when the associated on-otf valve is closed.

References Cited UNITED STATES PATENTS 562,410 6/1896 Moon 158118 2,022,481 11/ 1935 Schellenger 137-5 63 2,513,081 6/ 1950 Clark et al. 239-307 2,540,056 1/1951 Robinson 251286 2,618,576 11/1952 Brown et al. 117-104 2,672,844 3/ 1954 Flint 118-315 2,754,228 7/1956 Bede 117105.1 2,758,945 8/1956 Widmayer 117104 2,780,232 2/1957 Ney 251206 XR 2,827,260 3/1958 Jordan 251326 2,835,468 5/1958 Sparks 251-326 XR 2,838,066 6/1958 Harris 251-326 XR 2,883,148 4/ 1959 Williams 251-4105 2,893,893 7/1959 Crouse 11793 2,893,894 7/1959 Ransburg s 117 -93 2,915,023 12/ 1959 Rapaport 107-31 2,926,106 2/1960 Gauthier 118626 XR 2,937,656 5/1960 Evans et al 251-205 XR 2,951,499 9/1960 Singer 251-121 XR 3,055,592 9/ 1962 Probst 23915 CHARLES A. WILLMUTH, Primary Examiner. PETER FELDMAN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,377 ,987 April 16 1968 James W. Juvinall et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 11, "about .020 square" should read about .020 square Signed and sealed this 9th day of September 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR. 

1. A SYSTEM FOR PAINTING ARTICLES, AND COMPRISING AN ATOMIZING DEVICE FOR ATOMIZING PAINT SUPPLIED THERETO, MEANS TO PROVIDE A SUPPLY OF PAINT, A FLOW CONNECTION BETWEEN THE PAINT SUPPLY MEANS AND SAID ATOMIZING DEVICE, AN ADJUSTABLE OPEN ORIFICE VALVE IN SAID FLOW CONNECTION FOR CONTROLLING THE SUPPLY OF PAINT TO THE ATOMIZING DEVICE, SAID ORIFICE VALVE COMPRISING A PAIR OF MUTUALLY INTERRELATED AND RELATIVELY MOVABLE ORIFICE SIZING SURFACES FORMING THE ADJUSTABLE OPENING IN THE OPEN ORIFICE VALVE, MEANS FOR ADJUSTING SAID ORIFICE VALVE TO REGULATE THE FLOW OF PAINT THROUGH THE CONNECTION TO THE ATOMIZING DEVICE, AND MEANS IN SAID FLOW CONNECTION AND INDEPENDENT OF SAID OPEN ORIFICE VALVE AND OF SAID ATOMIZING DEVICE FOR INITIATING AND TERMINATING FLOW OF PAINT TO THE ATOMIZING DEVICE THROUGH SAID OPEN ORIFICE VALVE AND POSITIONED TO MAINTAIN A SUFFICIENT HEAD OF PAINT IN THE FLOW CONNECTION ON OPPOSITE SIDES OF THE OPEN ORIFICE VALVE BOTH TOWARD THE ATOMIZING DEVICE AND TOWARD THE PAINT SUPPLY MEANS FOR PROVIDING A QUIESCENT SUPPLY OF PAINT IN SAID OPEN ORIFICE VALVE COVERING SAID ORIFICE SIZING SURFACES WHEN THE INITIATING AND TERMINATING MEANS IS CLOSED, THEREBY TENDING TO PREVENT CLOGGING OF THE OPEN ORIFICE VALVE. 